Lean Combustion Stabilization via Pilot Fuel Injection Timing
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Solution Overview
Problem
The stability of main combustion in HCCI and CAI combustion processes is not consistently achieved due to variations in fuel distribution and temperature fluctuations, leading to uncontrollable ignition delay times and increased NOx emissions.
Innovation Solution
Introducing a pilot amount of fuel immediately after the gas exchange outlet valve closes, ensuring it is no more than 50% of the total fuel, and controlling the injection timing to achieve homogeneous distribution, which is influenced by temperature, pressure, and air ratio, thereby stabilizing the combustion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If pre-injection timing is advanced to ensure homogeneous fuel distribution, then fuel homogeneity is improved, but ignition delay time becomes uncontrollable due to premature fuel reaction
Solution Approach 1:
The patent applies preliminary action by performing pre-injection of fuel before the main compression stroke, during the intermediate compression phase. This timing allows the fuel to be introduced and distributed in the combustion chamber before the main compression and ignition events, ensuring homogeneous distribution while maintaining control over the ignition delay time through precise timing management of the pre-injection relative to the valve closing events.
2Stability of the object's composition
If EGR rate is increased to control combustion temperature, then combustion stability is improved, but valve timing complexity increases due to negative valve overlap requirements
Solution Approach 1:
The patent uses preliminary action by closing the gas exchange outlet valve before the gas exchange dead center (LWOT) to establish negative valve overlap in advance. This preliminary valve closing action creates the conditions for high EGR rates and intermediate compression, which stabilize the combustion process. The valve timing is predetermined and coordinated with the pre-injection timing to achieve the desired combustion stability without requiring complex real-time adjustments.
3Stability of the object's composition
If pre-injection quantity is increased to stabilize main combustion, then combustion stability is improved, but NOx emissions increase due to higher temperatures
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pre-injection quantity as a parameter that is optimized to stabilize main combustion while avoiding excessive temperature rise. The pre-injection quantity is set within specific ranges (e.g., 5-20% of total fuel quantity) and is coordinated with the intermediate compression temperature parameters to achieve combustion stability without generating excessive NOx emissions. This parameter optimization balances combustion stability with emission control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method stabilizes main combustion, expands the HCCI operating range, reduces NOx emissions, and minimizes combustion noise while allowing for lean-burn operation with various fuel qualities, eliminating the need for complex exhaust gas aftertreatment.
Implementation Method 1
introducing a pilot amount of fuel in intermediate compression no later than LWOT and compressing the pilot amount of fuel and a residual exhaust gas in the cylinder to form intermediate and complete combustion products
Implementation Method 2
compressing the pilot amount of fuel and a residual exhaust gas in the cylinder to form intermediate and complete combustion products
Implementation Method 3
Compressing the fresh gas and the fuel in the main compression phase
Implementation Method 4
Ignition of a mixture of fresh gas and fuel formed in the combustion chamber
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a lean combustion method for a four-stroke reciprocating internal combustion engine having a cylinder, in which a combustion chamber is delimited by a cylinder head and a piston that can be moved in a reciprocating manner, the piston being able to vary the volume of the combustion chamber and wherein a fuel can be introduced directly into the combustion chamber, wherein at least one gas exchange inlet valve and one gas exchange outlet valve are provided for a gas exchange, and wherein an intermediate compression can be set in the combustion chamber at a gas exchange top dead center (LWOT) and a main compression can be set at an ignition top dead center (ZOT).